@ApiMethod(summary = APIDoc.SUM_LIST_KNOWLEDGE, responsestatuscode = APIDoc.STATUS_LIST_KNOWLEDGE)
 @RequestMapping(value = "/user/{idUser}/knowledge", method = RequestMethod.GET)
 public HttpEntity getKnowledgesByUser(@PathVariable("idUser") Long idUser) {
   List<KnowledgeMod> knowledges = service.listKnowledgesByUser(idUser);
   if (knowledges.isEmpty()) return new ResponseEntity(HttpStatus.NO_CONTENT);
   else return new ResponseEntity(knowledges, HttpStatus.OK);
 }